To put an end to a joke, taking a joke too far and by that stopping people from laughing. Often causes people to feel uncomfortable

mid conversation between Livvy and Grace
Ruth: hey look guys i have a timer on my phone since Grace last shaved her legs, its been 32 hours
Livvy: That's hilarious ruth imagine if you kept it for 10 years
Grace: That would be hilarious
Ruth: yeah and like imagine it's 75th anniversary!!!
Livvy and Grace are silenced because the joke was 'ruthed'